Prominent among the changes are six more routes were added to the list of those that run every 15 minutes during peak times. Now, a dozen routes feature that frequency.

The most recent round of increased frequencies and extended service hours were enacted by The Rapid in January. In this round, six routes will feature increased frequency.

"This tends to be the most important and effective enhancement we can provide to our riders," said Peter Varga, CEO of The Rapid, arguing the increased frequency translates to bettered rider comfort and convenience.

The changes come as the Interurban Transit Partnership, which operates The Rapid in Grand Rapids and five adjacent communities, faces the possibility of a drastic change to its service area.

Walker city commissioners will consider a resolution at their meeting tonight that would certify the measure to appear on the city's November ballot. One of the route upgrades enacted Monday impacts a route that runs through part of Walker.

The Alliance has pointed to Walker voters' rejection of May 2011's narrowly passed millage that allowed for the service upgrades to be implemented this year as reason the city should abolish The Rapid's taxing authority there.

But last week, Friends of Transit/Walker announced its formation and counter-campaign to keep The Rapid running, calling the service a community staple that helps people get to work and travel throughout Greater Grand Rapids.

Under the upgrades, the following routes will go from 30-minute to 15-minute peak service frequency, according to The Rapid:

• Route 5 (Wealthy/Woodland) from Rapid Central Station on Grandville Avenue to Breton Village Mall at Breton Avenue and Burton Street

The Rapid noted 30-minute service will be maintained for portions of the above routes not specifically listed.

What's more, The Rapid announced 15-minute service along the Michigan Street corridor, served now by Route 13, through a new Route 19.

Route 19 "will mimic Route 13 between Rapid Central Station and the intersection of Michigan and Fuller," according to The Rapid. "Route 13 will continue to operate north of Michigan as it currently does. Route 19 will serve Fuller to the south until it reaches Hall Street. Both Routes 13 and 19 will have 30-minute peak frequency from the intersection of Michigan and Fuller through the end of the routes."

Other upgrades rolled out Monday include all routes operating on a base frequency of 30 minutes from 5 a.m. to 7:15 p.m.

That is possible by changing Route 17, which runs between Woodland Mall and Gerald R. Ford International Airport, and Route 44 along 44th Street from 60-minute service to 30 minutes.

The Rapid noted ridership is up nearly 39 percent after the service changes took effect earlier this year. Those figures do not include contract services, such as free rides for Grand Valley State University students, according to The Rapid.